Opened 3 years ago

Closed 3 years ago

#20361 closed defect (fixed)

PPL backend re-solves the problem every time get_variable_value or get_objective_value is called

Reported by: mkoeppe Owned by:
Priority: major Milestone: sage-7.2
Component: numerical Keywords: lp
Cc: dimpase, vdelecroix, jdemeyer Merged in:
Authors: Matthias Koeppe Reviewers: Dima Pasechnik
Report Upstream: N/A Work issues:
Branch: df42b5b (Commits) Commit: df42b5b74f30f1fca6a7c236c933c83b434f6f3e
Dependencies: Stopgaps:

Description

The PPL backend sets up a new PPL problem and re-solves it from scratch every time that get_variable_value or get_objective_value is called. 

sage: p = MixedIntegerLinearProgram(solver='ppl', maximization=True)
sage: x = p.new_variable()
sage: p.set_objective(p.sum((i+20)*x[i] for i in range(1000)))
sage: p.add_constraint(p.sum((i+15)*x[i] for i in range(1000)), max=20000)
sage: x.set_max(1)
sage: p.solve()  # takes a few seconds
11438750/507
sage: p.get_objective_value()  # takes a few seconds, should be instant
11438750/507
sage: p.get_values(x)  # takes forever, should be instant

Change History (5)

comment:1 Changed 3 years ago by dimpase

oh, great catch, I was always wondering why get_values is so bloody slow with ppl...

comment:2 Changed 3 years ago by mkoeppe

  • Branch set to u/mkoeppe/ppl_backend_re_solves_the_problem_every_time_get_variable_value_or_get_objective_value_is_called

comment:3 Changed 3 years ago by mkoeppe

  • Commit set to df42b5b74f30f1fca6a7c236c933c83b434f6f3e
  • Status changed from new to needs_review

New commits:

​df42b5bFix for #20361: PPL backend re-solves the problem every time get_variable_value or get_objective_value is called

comment:4 Changed 3 years ago by dimpase

  • Authors set to Matthias Koeppe
  • Reviewers set to Dima Pasechnik
  • Status changed from needs_review to positive_review

Great!

comment:5 Changed 3 years ago by vbraun

  • Branch changed from u/mkoeppe/ppl_backend_re_solves_the_problem_every_time_get_variable_value_or_get_objective_value_is_called to df42b5b74f30f1fca6a7c236c933c83b434f6f3e
  • Resolution set to fixed
  • Status changed from positive_review to closed
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